This invention relates to a fibre opening device for use in a discontinuous spinning process and particularly, although not exclusively, to a fibre opening device for an open end spinning machine.
In an open end spinning machine, the flow of fibrous material from feed sliver to yarn is interrupted in that the fibres are fed to a fibre opening device in the form of a rotatably mounted opening roller having a cylindrical working surface around which fibre opening elements are provided. The fibre opening elements may be integrated with the working surface or attached thereto, for example, in the form of carding wire. The fibre opening device separates the fibres of the sliver, the separated fibres then being transferred to a spinning rotor.
The Applicant has noted that, towards the outer edges of the cylindrical working surface of a fibre opening device, the fibre sliver tends to ride up away from the fibre opening elements and, in some cases, the sliver rides up over parts of the opening device which are disposed adjacent to the outer edges of the working surface. Thus, in use, fibres which are disposed towards the outer edges of the working surface are not separated fully and this may lead to defects in the yarn quality.
It is an object of the present invention to alleviate this problem.
Another factor which affects the quality of fibre produced in open end spinning is the presence of microdust in the spinning rotor. Microdust, which is believed to comprise small particles which are torn from the fibres themselves, may gradually build up between adjacent fibre opening elements on the working surface of the opening device. In this case, the presence of microdust may reduce the effectiveness of the opening elements in separating fibres. Furthermore, microdust may gradually be deposited in the groove of a spinning rotor which may consequently reduce the effectiveness of the spinning rotor and the quality of the yarn formed therein.
Many attempts have been made to reduce the level of microdust. For example, European Patent Application No. 0 348 178 (Stewart) discloses a fibre opening device for use with a discontinuous spinning process, the device comprising a rotatably mounted hollow opening roller having a cylindrical working surface from which fibre opening elements project. Holes, which are interspersed with the fibre opening elements, extend through the working surface of the roller and communicate with a hollow region within the roller. A vacuum suction device and a compressed air jet device, provided in the hollow region, are operated when necessary to remove dust, trash and short fibres which pass through the holes in the working surface and which would otherwise remain adhered to an interior cylindrical surface of the opening roller.